AQA GCSE National Grid

National Grid

The National Grid is a network of transformers and cables that will distribute electricity from power stations to consumers such as homeowners, factories and offices.

The power station produces an alternating potential difference of 25kv, or 25000v. Electricity from the power station will then be passed to a step up transformer

At the step up transformer the potential difference of the electricity is increased from 25,000v to 400,000v.

This allows the electricity to be transmitted as a high potential difference, low current.

Before the electricity reaches consumers such as homes it will pass through a step down transformer where the potential difference is reduced down to 230v for homes.

Why do we transmit the electricity with a high potential difference?

Electricity transmission is more efficient if a large potential difference is used, because it means a smaller current will flow.

Remember the equation Power = potential difference x current?

A large potential difference means that a small current is needed to transfer the same amount of electrical power.

If we now use another equation, for heat loss which links power, current and resistance:

Power = current² x resistance

The smaller the current, the smaller the power loss due to resistance heating in the electrical cables.

Overall, using high potential difference, low current allows the transmission of electricity to be efficient.